Mobile communication systems have been developed into high-speed, high-quality wireless packet data communication systems that provide a data service and a multimedia service in addition to the traditional voice-oriented service. To support high-speed, high-quality wireless packet data communication services, Code Division Multiple Access (CDMA) networks that provide 2nd Generation (2G) mobile communication have evolved into various mobile communication systems including High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Long Term Evolution (LTE), and LTE-Advanced (LTE-A) of the 3rd Generation partnership project (3GPP), and High Rate Packet Data (HRPD) of the 3GPP2.
Due to a rapid increase in the number of wireless communication users and increasing demands for large wireless communication capacities, legacy mobile communication systems, for example, the LTE communication system has limitations in accommodating increasing data traffic. In this context, direct communication between mobile terminals or User Equipments (UEs) (hereinafter, referred to as Device to Device (D2D) communication) without the intervention of an Evolved Node B (eNode B or eNB) has been introduced. Since direct communication is enabled between adjacent UEs by D2D communication, the UEs take over data transmission and reception control from an eNB, thus distributing the communication load of the eNB. Further, as adjacent UEs communicate with each other by D2D communication, the UEs may communicate faster on a better-quality channel than a channel between an eNB and a UE.
For the convenience in description, ● denotes a UE that supports both of D2D communication and mobile communication (hereinafter, referred to as a ‘D2D UE’ or a ‘dual mode UE’) and ∘ denotes a UE that supports only mobile communication (hereinafter, referred to as a ‘mobile UE’ or a ‘cellular UE’) in FIGS. 1A, 1B, 2A, and 2B. In the present disclosure, the ‘mobile communication’ may mean at least one of cellular communication (e.g., LTE communication, LTE-A communication, HSDPA communication, global system for mobile communication (GSM) communication, and wideband code division multiple access (W-CDMA) communication, etc.). In the present disclosure, the ‘D2D communication’ may mean at least one of WiFi communication, Bluetooth communication, and ZigBee communication, etc.
FIG. 1A illustrates an example of DownLink (DL) communication in a mobile communication system supporting D2D communication according to the related art.
Referring to FIG. 1A, UEs within the cell coverage of an eNB 110 may conduct D2D communication and mobile communication. Then the eNB 110 may transmit DL data for mobile communication on a DL channel to any of D2D UEs and mobile UEs.
FIG. 1B illustrates an example of UpLink (UL) communication in a mobile communication system supporting D2D communication according to the related art.
Referring to FIG. 1B, an eNB 120 may receive UL data for mobile communication from any of D2D UEs and mobile UEs.
FIG. 2A illustrates an example of D2D communication during DL communication in a mobile communication system supporting D2D communication according to the related art.
Referring to FIG. 2A, while an eNB 210 is conducting DL communication with a mobile UE, a D2D UE 211 may directly communicate with another D2D UE by D2D communication. It is assumed herein that the D2D UE 211 has requested D2D communication to the eNB 210 and the eNB 210 has accepted the D2D communication request.
FIG. 2B illustrates an example of D2D communication during UL communication in a mobile communication system supporting D2D communication according to the related art.
Referring to FIG. 2B, while an eNB 220 is conducting UL communication with a mobile UE, a D2D UE 221 may directly communicate with another D2D UE by D2D communication. It is assumed herein that the D2D UE 221 has requested D2D communication to the eNB 220 and the eNB 220 has accepted the D2D communication request.
To conduct D2D communication as well as mobile communication with an eNB in the mobile communication system as illustrated in FIGS. 2A and 2B, a D2D UE includes a transceiver for distinguishing the communication schemes, that is, mobile communication and D2D communication from each other. The transceiver includes duplexers for inputting and outputting signals by distinguishing mobile communication from D2D communication and a plurality of Radio Frequency (RF) chains mapped to the respective duplexers, for processing transmission and reception signals.
In general, an RF chain includes amplifiers, mixers, and converters. The amplifiers include a Power Amplifier (PA) that amplifies the strength of a signal and a Low Noise Amplifier (LNA) for amplifying a signal by reducing noise. The mixers include an up mixer for upconverting a baseband signal into an RF signal and a down mixer for downconverting an RF signal into a baseband signal. The converters include a Digital to Analog Converter (DAC) for converting a digital signal into an analog signal and an Analog to Digital Converter (ADC) for converting an analog signal into a digital signal.
In general, a duplexer includes an antenna and two band pass filters for filtering a signal received through the antenna and filtering a transmission signal from a signal amplified by an amplifier.
FIG. 3 is a block diagram of a UE operating in a mobile communication system supporting D2D communication according to the related art.
Referring to FIG. 3, a UE 300 operates, for example, in Frequency Division Duplexing (FDD) and includes first and second duplexers 310 and 340 for respective communication schemes, a plurality of antennas 311 and 341, a plurality of RF chains, and a controller 370. Each of the plurality of RF chains includes a Transmission (Tx) chain for processing a signal to be transmitted to a wireless network and a Reception (Rx) chain for processing a signal received from the wireless network, in a communication scheme corresponding to the RF chain.
The UE 300 includes the first duplexer 310 for mobile communication and the second duplexer 340 for D2D communication. The first duplexer 310 includes two duplexers, one of which is connected to a first Tx chain 320 for processing a signal to be transmitted to an eNB and the other of which is connected to a first Rx chain 330 for processing a signal received from the eNB.
Likewise, the second duplexer 340 includes two duplexers, one of which is connected to a second Tx chain 350 for processing a D2D communication signal to be transmitted to a D2D UE and the other of which is connected to a second Rx chain 360 for processing a D2D communication signal received from the D2D UE.
Each of the first and second Tx chains 320 and 350 includes an amplifier 321 or 351, a mixer 322 or 352, and a Digital-to-Analog Converter (DAC) 323 or 353. Likewise, each of the first and second Rx chains 330 and 360 includes an amplifier 331 or 361, a mixer 332 or 362, and an Analog-to-Digital Converter (ADC) 333 or 363.
The controller 370 conducts mobile communication by controlling the first Tx and Rx chains 320 and 330 and D2D communication by controlling the second Tx and Rx chains 350 and 360. Detailed operations of each Tx chain and each Rx chain are known and will not be described herein.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.